Side effects might include daytime drowsiness, dry mouth and dizziness.Also, diphenhydramine and doxylamine — sedating antihistamines often found in over-the-counter sleep aids — aren't recommended for people who have certain conditions, such as closed-angle glaucoma, asthma, chronic obstructive pulmonary disease or severe liver disease.
These symptoms may be due to hay fever, other upper respiratory allergies, or common cold.
Benadryl can also be used to treat hives and to reduce redness and itching.
They're usually divided into two main groups: They also come in several different forms – including tablets, capsules, liquids, syrups, creams, lotions, gels, eye drops and nasal sprays.
There's not much evidence to suggest any particular antihistamine is better than any other at relieving allergy symptoms.
Antihistamines are those drugs that block the H1 histamine receptors and not the other histamine receptors like H2, H3 and H4. These drugs act by block the histamine-induced responses in allergic reactions.
It is the most widely used allergy medicine for most of the common allergic diseases.
Non-drowsy antihistamines are generally the best option, as they're less likely to make you feel sleepy.
But types that make you feel sleepy may be better if your symptoms affect your sleep.
Although the sedative effect of antihistamines are sometimes desired, like in a patient with allergic rhinitis who is having difficulty sleeping, generally the use of these drugs should be limited in a person who is driving or operating heavy machinery.
Some of the first generation antihistamines also block other receptors like cholinergic (muscarinic) receptors and alpha adrenergic receptors.
A strong sedative effect of the older first generation antihistamines is one of the most distinguishing features between the two groups.